(On my Eee 1005HAB netbook, with 2 GB of RAM and an Atom n270. Yes, I know. I could use it on my AMD A2 workstation with 8 GB of RAM, but everything runs fast on that thing. Anyway...) Under Linux: The Firefox GUI gets laggy whenever there's rendering in progress, or at random intervals when Firefox decides to start hogging CPU for inscrutable reasons. Toggling hardware accel doesn't seem to make a difference. Under Windows: Wow. If it was slow on Linux, that's nothing to what it's like on Windows. I type in "duckduckgo.com" and it's like "d... u... c... kduc... k... g..." I right-click on a page, and the menu shows up blank for several seconds before the menu entries start to render. It's like watching a slide show. Again, hardware accel on or off makes no difference. Neither does turning Win7 Aero glitz off. Now here's the interesting thing though: Seamonkey is fast. Fast! It renders pages visibly faster, and the GUI only lags on truly bloated sites like GMail. It also uses perhaps 100 MB less resident memory on startup than Firefox does. And there are no weird CPU spikes when it ought to be idle, either. ... And yeah, I'm pretty sure now that it's the new GUI. This sluggishness seems to apply to all versions of Firefox and Iceweasel with the Australis theme. Seamonkey doesn't have the theme... and it's fast. I'm going to see if disabling certain Firefox theme features can restore the snappy. Gimme a few minutes...
Hmm. Classic Theme Restorer extension does seem to help quite a bit. I think part of the issue is that the new main menu, for some reason, is slow and expensive to render.
FYI. My FF 41.0.2 works fast with the Aurora Australis theme in Win7 64-bit. Have you tried switching to Default?
Eh? Oh... No no no, when I say "Australis" I mean the default theme for Firefox 40+. With the new popup config panel and all.
Nope, and I probably won't. A fork of an old version of Firefox, maintained by a small team, does not strike me as a good thing to be using for day-to-day browsing. (Linus' Law is largely incorrect, but its inverse need not be.) ... In any case, my current workaround for Firefox is more of a brain hack - I have it set to switch to new tabs immediately. This obviously doesn't improve responsiveness, but it discourages multitasking within the Firefox window, which reduces the impact of the lag (and is probably a better habit anyway).
